It is known that most aircraft currently in service, in particular civil transport planes, are equipped with onboard electronic devices, in particular computers of so-called “avionics type”. These electronic devices are used, in particular, for the aircraft's strategic flight functions such as the flight controls. These devices have, consequently, to exhibit a very high level of reliability, able to guarantee a failure rate of the aircraft that is lower than that demanded by the certifying authorities. The communication networks and the links between such onboard devices (computers) of avionics type must meet the same reliability demands.
Certain modern transport planes, such as planes of the “Airbus A340-600” and “Airbus A318” type for example, also comprise so-called “open world” onboard equipment, which is not specific to aeronautical applications. This “open world” equipment is interface means (of “man-machine” type ) available to an operator, in particular a pilot, of the airplane. By way of nonlimiting example, mention may be made of so-called industrial processors, portable computers, printers, etc. Such “open world” equipment exhibits a lower level of reliability than that of the aforementioned devices of avionics type. It nevertheless has the advantage of being much cheaper than them and its reliability level is sufficient for applications that are not directly related to maneuvers of the plane, such as for example the consulting of maintenance documentation or diagnostic aid with regard to maintenance. When an airplane comprises interface means of open world type, it is sometimes beneficial to be able to use one or more of these interface means, to allow an operator to exchange information with devices of avionics type. This may be useful in particular within the framework of maintenance operations on the airplane, for consulting values of parameters available in devices of avionics type or for testing certain components of the airplane (for example electrical circuits, control surfaces, etc). the maneuvering of which is controlled by such devices of avionics type.
However, even if these maintenance operations exhibit lesser criticalness than that of the flight phases of the airplane, the reliability level of said interface means of open world type may not be sufficient in certain cases. Thus, by way of example, when a maintenance operation involves the maneuvering of a control surface, it is imperative for the latter not to trigger inadvertently, since inadvertent triggering could be dangerous for personnel located in proximity to said control surface. Likewise, when a maintenance operation entails the handling of electrical equipment, the operator must ensure that this equipment is not live, erroneous information possibly having fatal consequences.
Consequently, it is generally strongly discouraged, in particular for reliability and hence safety reasons, to implement transmission of sensitive information on an aircraft between a device of avionics type, such as described above, and an interface means of aforesaid type.